Device and method for reshaping bar-shaped materials particularly for drawing and extruding

ABSTRACT

An apparatus for reforming rod-shaped, electrically conductive and/or magnetizable materials, in particular for drawing and extruding, having the following features: the apparatus has a female mold having a die, which forms the tool for reforming; the apparatus has an inductor of an electric linear motor, by means of which a traveling electric field can be produced; the inductor includes at least one first group at least with first coils; the first coils in the first group are arranged axially next to one another and thus form a channel; using the inductor it is possible to produce a traveling field in the channel which has a magnetic flux density having a gradient in the axial direction of the channel, which has an amplitude of greater than B=1 T.

BACKGROUND OF THE INVENTION

This application is a 35 USC 371 of PCT/03965 filed Oct. 21, 2002.

The invention relates to an apparatus and a method for reformingelectrically conductive and/or magnetizable, rod-shaped materials, inparticular for drawing and extruding.

Such an apparatus has a female mold having a die, which forms the toolfor reforming. In addition, the apparatus has an inductor of an electriclinear motor. This inductor has at least one first group at least withfirst coils, these first coils in the first group being arranged axiallynext to one another, and the center, which remains free, of the coilsforming a channel. The rod-shaped material, which is to be reformed andwhich is electrically conductive and magnetizable, is introduced intothis channel. This rod-shaped material forms the armature of the linearmotor. Owing to the fact that a traveling magnetic field is produced inthe channel of the inductor by the inductor, the armature, i.e. therod-shaped material, is moved on in the channel. In the process, with anappropriate rating for the inductor, the rod-shaped material can bemoved through the die of the female mold, as a result of which therod-shaped material is reformed.

Such an apparatus is known, for example, from the document U.S. Pat. No.3,911,706 A. The document discloses a linear drawing machine for drawinga rod-shaped material through the die of a female mold. For thispurpose, the inductor is arranged such that it lies downstream of thedie in the drawing direction. The rod-shaped material which isintroduced into the die in a manner which is not disclosed in any moredetail is passed through the inductor downstream of the die in thedrawing direction, as a result of which the in-ductor, in interactionwith the rod-shaped drawing material which acts as the armature, forms alinear motor which draws the rod-shaped drawing material through the dieand thus reforms it.

The disadvantage of the drawing machines disclosed in this document isthe fact that the forces produced by the inductor in interaction withthe drawing material are only sufficient for a reforming process, inparticular for larger drawing materials, if the inductor, i.e. thedrawing machine, has a length of several hundred meters. Such a drawingmachine, however, is unrealistic since it cannot be produced andoperated at reasonable cost.

Owing to the abovementioned disadvantages, the development of such alinear drawing machine has not been pursued further up until now.Rather, development work has been concentrated on the improvement ofconventional linear drawing machines. Such a conventional drawingmachine is known, for example, from the document DE 197 03 878 A1. Thelinear drawing machine disclosed in this document has two moveabledrawing carriages which are driven on a track, each drawing carriagehaving associated travel paths, which lie one behind the other in thedrawing direction but which partially overlap one another. These drawingcarriages, whose travel paths are both provided downstream of the die inthe drawing direction, have clamping jaws. The two drawing carriages,alternately, use these clamping jaws to draw the drawing materialthrough the die. The drawing carriages are in this case provided withconventional drive means, i.e. either such drawing carriages havededicated drives, usually electric motors, or else they are driven bymeans of transmission devices of a common drive for both drawingcarriages. Although the drive and the control of the drawing carriageswhich are matched to one another are complex, a lack of alternatives hasmeant that this technique has been adopted in the past in the case oflinear drawing machines, since the drawing could not be convertedexpediently by means of the basically simple drive technology disclosedin the document U.S. Pat. No. 3,911,706 A.

The present invention was therefore based on the object of developing alinear drawing machine known from the document U.S. Pat. No. 3,911,706 Asuch that expedient use of a linear drawing machine according to theinvention is possible. In particular, in the process the apparatusaccording to the invention should have smaller dimensions than theapparatus known from the prior art.

A further concern of the present invention was also to make it easier tointroduce the material to be reformed into the die of the female mold.It should likewise be possible to use the apparatus according to theinvention not only to reform the rod-shaped material by means ofdrawing, but also by extruding the rod-shaped material to be reformedthrough the die of the female mold of the apparatus.

SUMMARY OF THE INVENTION

The objects according to the invention are achieved by an apparatus andmethod for reforming rod-shaped, electrically conductive and/ormagnetizable materials, which remedies the disadvantages of the methodsknown from the art.

The apparatus according to the invention and the method according to theinvention are based on the knowledge that the magnetic flux density,which is present in the channel of the apparatus known from the closestprior art (cf. U.S. Pat. No. 3,911,706 A) is insufficient to makepossible an apparatus of compact size having sufficient performance. Inorder to have at one's disposal an apparatus having sufficientperformance, i.e. in particular sufficient development of force, thisapparatus must be able to produce, according to the invention, atraveling magnetic field in the channel formed by the inductor which hasa magnetic flux density having an amplitude of greater than B=1 tesla.Depending on the movement direction of the traveling magnetic field, inthis case a force in the direction towards the die or away from the diecan be utilized by the interaction between the inductor and the materialto be reformed (armature). In the case of a force direction towards thedie, this force may cause the material to be introduced into the dieand/or the apparatus to be used for extrusion purposes. For extrusionpurposes, in this case it is merely advantageous for the die to bearranged in the opposite direction with respect to the first group ofcoils to that for drawing.

In accordance with the invention, the inductor of an apparatus accordingto the invention may have a second group at least with first coils. Thefirst group of coils and the second group of coils can thenadvantageously be arranged on opposite sides of the female mold, thecoils in the two groups then preferably being coaxial with respect tothe die of the female mold. With such an arrangement of the coils of theinductor in two groups in the transport direction of the rod-shapedmaterial to be reformed upstream and downstream of the die of the femalemold, it is possible both to push the material being transported throughthe die and to draw the rod-shaped material to be reformed through thedie of the female mold. Drawing and extrusion may in this case takeplace independently of one another, i.e. the rod-shaped material iseither exclusively extruded or else exclusively drawn. However, it islikewise possible for the drawing and extrusion to take place at thesame time, i.e. the coils in the second group, which are arrangedupstream of the female mold in the transport direction of the rod-shapedmaterial, bring about extrusion, whereas, at the same time, the coils inthe first group, which are arranged downstream of the female mold in thetransport direction, bring about drawing of the rod-shaped material.With such an apparatus for simultaneous drawing and extrusion, greaterreforming of the material to be reformed is possible.

In accordance with the invention, the first group and possibly thesecond group of coils of the inductor may have second coils, thesesecond coils engaging around the first coils and being arrangedcoaxially with respect to the first coils. In addition, further coils,namely third, fourth, . . . coils may be provided which engage aroundthe coils in the first and possibly the second group and are coaxialwith respect to the second, third, . . . coils. The arrangement of thesecond, third, . . . coils makes it possible for the magnetic fluxdensity in the channel to be increased. Such inductors are sometimesknown as polysolenoid inductors.

In accordance with the invention, in each case disks made of amagnetizable material, which may possibly be perforated, are arrangedbetween the coils which are arranged coaxially next to one another. Inthese disks, the magnetic flux produced by the coils can be combined.The disks may have an outer edge which is advantageously bent back toone side. This bent-back edge may then cover an adjacent, first coil ora stack of adjacent and coaxially arranged coils (first, second, third,. . . coils). Such coil/disk arrangements are also known as “pancake”arrangements.

In accordance with the invention, the apparatus may have means forcooling the rod-shaped material to be reformed. The means for coolingcan apply a first cooling medium to the channel in which the rod-shapedmaterial to be reformed is transported. This first cooling medium may beair or oil or another suitable cooling medium. In this case, it issufficient if the cooling medium has a temperature of 0 to 40° C.,preferably room temperature.

The electrical current density in the coils is advantageously greaterthan J=10 A/mm², in order to achieve a compact design.

In accordance with the invention, at least some of the coils may haveconductors which have a resistivity of ρ=0.017*10⁻⁶ Ωm or less. Some ofthe coils may likewise have conductors which are superconducting. Inaccordance with the invention, superconducting conductors may be made ofa material which has a critical temperature of greater than T=77 K. Inaddition, some of the coils may have conductors which have a channel, asa result of which the conductor is in the form of a hollow conductor. Asecond cooling medium can be applied to such a channel in a conductor.As a result, the conductors can be cooled down in order to increase theelectrical conductivity of the conductor. Such a conductor having achannel is advantageously produced from silver, gold, but preferablyfrom copper or aluminum. Water, oil, liquid nitrogen, hydrogen or neonare advantageously used as the cooling medium for the purpose of coolingthis conductor from the inside.

In a method according to the invention, in one step, the material to bereformed is introduced into the channel; in a further step, a travelingmagnetic field having a magnetic flux density of at least B=1 T isproduced in the channel and has a gradient in the direction of thechannel; and, in another step, the material to be reformed is introducedinto the die of the female mold. The sequence of the steps can in thiscan be varied in any desired manner. It is likewise possible for thestep which comprises the introduction of the material to be reformed tobe split into two substeps. It is likewise possible for the step whichcomprises the production of the traveling field to be split into twoparts. Even if this step is split into two parts in this manner, thesequence of the (sub)steps can in principle be combined in any desiredmanner.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the present invention are made clearusing the description below of preferred exemplary embodiments withreference to the attached drawings, in which:

FIG. 1 shows a schematic illustration of an apparatus according to theinvention,

FIG. 2 shows a schematic, sectioned illustration through the inductor ofan apparatus according to the invention,

FIG. 3 shows a schematic illustration of an apparatus according to theinvention for drawing,

FIG. 4 shows a schematic illustration of an apparatus according to theinvention for extruding, and

FIG. 5 shows a schematic illustration of an apparatus according to theinvention for drawing and extruding.

DETAILED DESCRIPTION OF THE INVENTION

Firstly, reference is made to FIG. 1. The apparatus 1 according to theinvention which is illustrated schematically in FIG. 1 and is used fordrawing a rod-shaped material 2 has a female mold 3 having a die 4 whichtapers in the movement direction of the material 2. An inductor 5 isarranged downstream of the female mold 3 in the movement direction ofthe material 2. This inductor 5, together with the material 2 which iselectrically conductive and/or magnetizable, forms an electric linearmotor, the rod-shaped material 2 to be reformed forming the armature ofthe linear motor. The rod-shaped material 2 is generally a tube, whoseouter cross section has been reduced in size.

The inductor 5 has a plurality of first electrical coils 8, in the caseof which the windings from one conductor 9 are arranged on a plane whichlies perpendicular to the movement direction of the rod-shaped material2. In this case, the electrical conductor 9 is embedded in a diskcomprising an isolator 13. The centers, which remain free, of thesedisks formed from the isolator 13 or of the coils 8 form a channel 12which is axial with respect to the movement direction of the rod-shapedmaterial 2 and axial with respect to the die 4.

Disks 10 made of a magnetizable material 10 are arranged between thedisks comprising the isolator 13 which contain the coils 8. These disks10 have an outer edge 11 which is bent back to one side. This bent-back,outer edge 11 of the disks 10 covers an adjacent coil.

The coil/disk arrangements illustrated in FIG. 1 which essentially formthe inductor 5 are arranged downstream of the female mold 3 in themovement direction of the rod-shaped material 2, as a first group 6 offirst coils 8. A traveling electrical field is produced by means ofthese coils 8 in the first group 6, and this traveling electrical fieldpredetermines the movement direction of the rod-shaped material 2. Thetraveling magnetic field, which is passed, inter alia, into themagnetizable disks 11, has a magnetic flux density of at least 1 T inthe center of the channel 12 formed by the inductor 5. This travelingmagnetic field produces rotational electrical fields in the rod-shapedmaterial and thus a current flow in the rod-shaped material 2. In turn,this current flowing in the rod-shaped material 2 produces a magneticfield which interacts with the traveling magnetic field which isproduced by the inductor 5, and, as a result, a force in the directionof the traveling magnetic field is applied to the rod-shaped material 2.

Since the traveling magnetic field has a magnetic flux density of atleast 1 T in the center of the channel 12, only compact inductors 5having a manageable size are required for the application of the forcesrequired for drawing the rod-shaped material 2 through the female mold3.

The conductors 9 of the first coils 8 illustrated in FIG. 1 areconductors 9 which have an inner channel. These electrical conductors 9are thus in the form of hollow conductors. Using means for cooling (notshown), a first cooling medium can be passed through the channels of theconductors 9, and this first cooling medium cools the electricalconductors 9 from the inside. Cooling of the electrical conductorsbrings about a significant increase in the electrical conductivity.

With the cross section illustrated in FIG. 2 through the inductor 5 ofan apparatus 1 according to the invention, the same reference numeralshave been used for equivalent components as for the apparatus 1according to the invention shown in FIG. 1. The inductor 5 shown in FIG.2 differs from the inductor 5 illustrated in FIG. 1 only by theformation of the electrical conductors 9 of the first coils 8. In thiscase, the electrical conductor 9 is one which is made of asuperconducting material. By means of cooling (not shown), thiselectrical conductor 9 can be cooled to a temperature of approximately77° K. The superconducting material of the electrical conductor 9 thenreaches its critical temperature, as a result of which the electricalconductivity suddenly increases.

FIG. 3 is a schematic illustration of how, by means of an apparatusaccording to the invention, the material 2 to be reformed can bereformed by drawing. The apparatus according to the inventionillustrated in FIG. 3 has, for this purpose, a female mold 3 having adie 4, which is arranged upstream of an inductor 5 in the drawingdirection. The inductor 5 has coils 8, of which in each case only onewinding of the conductor 9 is illustrated schematically. The ends of theconductor 9 of the coils 8 are passed out of the inductor 5 and areconnected to an electrical voltage source 14 for the purpose ofsupplying a voltage to the coils 8. The coils 8 in this first group 6 ofcoils 8 are supplied by the voltage source 14 such that a travelingmagnetic field is produced in the inductor 5. The inductor 5 then acts,with a material 2 to be reformed introduced, as a linear motor, thematerial 2 to be reformed forming the armature of this linear motor.

For drawing purposes, firstly the voltage supply of the coils 8 in thefirst group 6 of coils 8 of the inductor 5 is accepted. The travelingmagnetic field is produced. Then, the material 2 to be reformed isintroduced into the die 4 of the female mold 3 using methods known fromthe prior art. As soon as the end of the material 2 to be reformedemerges from the die 4, the material 2 to be reformed is introduced intothe inductor 5, as a result of which a force, which is produced by thetraveling magnetic field in interaction with the material 2 to bereformed, is applied to the material 2 to be reformed in the directionof movement or the drawing direction.

With reference to FIG. 4, an explanation will now be given of how theextrusion takes place using an apparatus according to the invention. Theapparatus illustrated schematically in FIG. 4 for extruding corresponds,in principle, to the design of the apparatus shown in FIG. 3. Incontrast to the apparatus illustrated in FIG. 3, the apparatusillustrated in FIG. 4 has the first group 6 of first coils 8 upstream ofthe female mold 3 having the die 4 in the movement direction of thematerial 2 to be reformed.

Firstly, with the apparatus according to the invention shown in FIG. 4,the production of the traveling magnetic field by means of the inductor5 is introduced by switching on the voltage sources 14. Then, thematerial 2 to be reformed is introduced into the inductor 5, as a resultof which the abovedescribed interaction between the inductor 5 and thematerial 2 to be reformed 2 comes about which pushes the rod-shapedmaterial 2 to be reformed in the movement direction of the travelingfield. As a result, the material 2 to be reformed is pushed in thedirection of the female mold 3 and introduced into the die 4 of thefemale mold 3. The force, which is applied by the linear motor formed bythe inductor 5 and the material 2 to be reformed, is in this casesufficient for pushing the material 2 to be reformed through the die 4.By extruding the material 2, the material 2 is reformed. In this case,the cross section of the material 2 is reduced.

With reference to FIG. 5, an explanation will now be given of how, usingan apparatus 1 according to the invention, a material 2 to be reformedcan be both extruded and drawn in order to reduce the cross section ofthis material 2. The apparatus according to the invention illustrated inFIG. 5 has, for this purpose, an inductor 5 having a first group 6 offirst coils 8 and a second group 7 of first coils 8. The electricalconductors 9 of these coils 8 are passed out of the inductor andconnected to an electrical voltage source 14. The coils in the firstgroup 6 are in this case arranged downstream of the female mold 3 havingthe die 4 in the movement direction of the material 2 to be reformed,whereas the coils in the second group 7 are arranged upstream of thefemale mold 3 having the die 4 in the movement direction.

In order to reform the rod-shaped material 2, the coils 8 in the firstgroup 6 and the coils 8 in the second group 7 have an electrical voltageapplied to them. As a result, a traveling field is produced in theinductor 5 which has a movement direction which predetermines themovement direction of the material 2 to be reformed. Subsequently, thematerial 2 to be reformed is introduced into the inductor 5. Therod-shaped material 2 in this case initially passes into the part of thechannel which is formed by the first coils 8 in the second group 7 ofcoils 8, and forms there the armature of a linear motor formed by theinductor 5. In this case, the material 2 to be reformed is pushedforwards in the movement direction by the force produced by the linearmotor and is introduced into the die 4 of the female mold 3. The forcewhich is produced by the coils 8 in the second group 7 in interactionwith the material 2 to be reformed pushes the material 2 to be reformedthrough the die 4 and, as soon as the material 2 to be reformed has leftthe die 4, the material 2 to be reformed enters the part of the channelformed by the coils 8 of the first group 6, where the material 2 to bereformed forms with this part of the inductor 5 a linear motor which inturn applies a force to the material 2 to be reformed in the movementdirection of the traveling field. As a result, both in the region offirst group 6 and in the region of the second group 7 of the first coils8, the material 2 to be reformed is subjected to forces.

The advantage of an apparatus 1 of this type for simultaneous drawingand extrusion is the fact that, in this case, no mechanical connectionis provided for the purpose of transferring the forces to the material 2to be reformed, i.e. there are no moveable parts (connection means)which are used for force transfer purposes. The problem with theconventional type of force transfer by means of mechanical connectionmeans to the material 2 to be reformed is the fact that the material tobe reformed can have different speeds upstream and downstream of the die4. These different speeds then need to be carefully controlled for anoptimum force transfer between the connection means and the material 2to be reformed. Such complex regulation is not required in the apparatusaccording to the invention, since in this case there is no mechanicalconnection between the connection means for driving the material 2 to bereformed and the material 2 to be reformed. The force transfer in facttakes place in this case by means of electromagnetic interaction betweenthe material 2 to be reformed and the inductor 5 of the apparatus 1according to the invention. The electromagnetic force transfer takesplace in contactless fashion, and at different speeds of the travelingmagnetic field of the inductor 5 and the material 2 to be reformed,there is a slip. Such a slip is also known, for example, from anasynchronous motor between the rotor and the stator. This slip may bedifferent in the region of the first group 6 of first coils 8, i.e. inthe region downstream of the die 4, than a slip in the region of thesecond group 7 of first coils 8, i.e. in the region upstream of the die4. Complex regulation for the purpose of compensating for the differentspeed of the material 2 to be reformed upstream and downstream of thedie 4 is thus dispensed with. Such an apparatus makes possible, in oneworking step, increased reduction of the material 2.

LIST OF REFERENCE NUMERALS

-   1 Reforming apparatus-   2 Material to be reformed-   3 Female mold-   4 Die-   5 Inductor-   6 First group of coils-   7 Second group of coils-   8 First coils-   9 Electrical conductor-   10 Disk-   11 Outer, bent-back edge-   12 Channel-   13 Isolator-   14 Electrical voltage source

1. An apparatus for reforming rod-shaped, electrically conductive and/ormagnetizable materials comprising: the apparatus has a female moldhaving a die, which forms a tool for reforming; the apparatus has aninductor of an electric linear motor, by means of which a travelingelectric field can be produced; the inductor comprises at least onefirst group at least with first coils; the first coils in the firstgroup are arranged axially next to one another and thus form a channel;using the inductor it is possible to produce a traveling field in thechannel which has a magnetic flux density having a gradient in the axialdirection of the channel; wherein the gradient has an amplitude ofgreater than B=1 T, and at least some of the first coils have aconductor which has a resistivity of ρ=0.017*10-6Ωm or less.
 2. Theapparatus as claimed in claim 1, wherein the inductor has a second groupat least with first coils.
 3. The apparatus as claimed in claim 2,wherein the first group and the second group are arranged on oppositesides of the female mold, the first coils of the two groups beingcoaxial with respect to the die of the female mold.
 4. The apparatus asclaimed in claim 2, wherein the first group and possibly the secondgroup have second coils, which engage around the first coils and arecoaxial with respect to the first coils.
 5. The apparatus as claimed inclaim 4, wherein the first group and the second group comprise aplurality of coils, which engage around the coils and are coaxial withrespect to the plurality of coils.
 6. The apparatus as claimed in claim1, wherein in each case a disk made of a magnetizable material isarranged between the first coils which are arranged coaxially next toone another.
 7. The apparatus as claimed in claim 1, wherein the have anouter edge which is bent back to one side.
 8. The apparatus as claimedin claim 7, wherein the bent-back edge covers an adjacent, first coil ora stack of adjacent and coaxially arranged coils.
 9. The apparatus asclaimed in claim 1, wherein the apparatus has means for cooling therod-shaped material to be reformed.
 10. The apparatus as claimed inclaim 9, wherein the means for cooling apply a first cooling medium tothe channel.
 11. The apparatus as claimed in claim 10, wherein the firstcooling medium is air or an oil.
 12. The apparatus as claimed in claim11, wherein the electrical current density in the first coils is greaterthan J=10 A/mm².
 13. The apparatus as claimed in claim 1, wherein atleast some of the first coils have conductors which are superconducting.14. The apparatus as claimed in claim 13, wherein the superconductingconductors are made of a material which has a critical temperature ofgreater than T=77 K.
 15. The apparatus as claimed in claim 1, wherein atleast some of the first coils have conductors which have a channel. 16.The apparatus as claimed in claim 15, wherein a second cooling mediumcan be applied to the channel in the conductor
 17. A method forreforming rod-shaped, electrically conductive and/or magnetizablematerials using the apparatus as claimed in claim 1, having thefollowing steps: Step a) in one step, the material to be reformed isintroduced into the channel; Step b) in one step, a traveling magneticfield having a gradient lying in the channel direction is produced inthe channel and has, in center of the channel, a magnetic flux densityhaving an amplitude of greater than B=1 T; and Step c) in one step, thematerial is introduced into the die of the female mold.
 18. The methodas claimed in claim 17, wherein step c) is performed, followed by stepa), and then followed by step b).
 19. The method as claimed in claim 17,wherein step c) is followed by step b), and followed by step a).
 20. Themethod as claimed in claim 17, wherein step a) is followed by step b),and followed by step c).
 21. The method as claimed in claim 17, whereinstep b) is followed by step a), and followed by step c).
 22. The methodas claimed in claim 17, wherein Step a1) in one step, the material to bereformed is introduced into a first part of the channel; Step a2) in onestep, the material is introduced into a second part of the channel; Stepb1) in one step, the traveling magnetic field is produced in the firstpart of the channel; and Step b2) in one step, the traveling magneticfield is produced in the second part of the channel.
 23. The method asclaimed in claim 22, wherein the steps are carried out in the followingsequence: Step a1), Step c), Step b1) ((+)) and Step b2).
 24. The methodas claimed in claim 22, wherein the steps are carried out in thefollowing sequence: Step b1) ((+)) and Step b2), Step a1), Step c), andStep a2).